Article

1H, 13C, and 15N resonance assignment of the central domain of hRSV transcription antitermination factor M2-1.

Unité de Virologie et Immunologie Moléculaires, INRA UR0892, 78350, Jouy-en-Josas, France.
Biomolecular NMR Assignments (Impact Factor: 0.64). 04/2011; 5(2):237-9. DOI: 10.1007/s12104-011-9308-3
Source: PubMed

ABSTRACT M2-1 is an essential co-factor of the respiratory syncytial virus, an important respiratory pathogen in infants and calves. It acts as a transcription antitermination factor which enhances the processivity of the polymerase. Within the polymerase complex, M2-1 interacts with a second co-factor, the phosphoprotein P. It has been shown previously that P and RNA bind to M2-1 in a competitive manner in vitro and that these properties are related to a central domain located between residues Glu59 and Lys177. Here we report the almost complete (1)H, (13)C and (15)N assignment of a fragment of M2-1 corresponding to this region, for further structure determination and interaction studies.

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    ABSTRACT: Respiratory syncytial virus (RSV) protein M2-1 functions as an essential transcriptional cofactor of the viral RNA-dependent RNA polymerase (RdRp) complex by increasing polymerase processivity. M2-1 is a modular RNA binding protein that also interacts with the viral phosphoprotein P, another component of the RdRp complex. These binding properties are related to the core region of M2-1 encompassing residues S58 to K177. Here we report the NMR structure of the RSV M2-1(58-177) core domain, which is structurally homologous to the C-terminal domain of Ebola virus VP30, a transcription co-factor sharing functional similarity with M2-1. The partial overlap of RNA and P interaction surfaces on M2-1(58-177), as determined by NMR, rationalizes the previously observed competitive behavior of RNA versus P. Using site-directed mutagenesis, we identified eight residues located on these surfaces that are critical for an efficient transcription activity of the RdRp complex. Single mutations of these residues disrupted specifically either P or RNA binding to M2-1 in vitro. M2-1 recruitment to cytoplasmic inclusion bodies, which are regarded as sites of viral RNA synthesis, was impaired by mutations affecting only binding to P, but not to RNA, suggesting that M2-1 is associated to the holonucleocapsid by interacting with P. These results reveal that RNA and P binding to M2-1 can be uncoupled and that both are critical for the transcriptional antitermination function of M2-1.
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